U.S. Pat. No. 4,721,498 discloses an endless elastomeric drive belt designed to minimize lateral shifting, having a first ply of wire cable reinforcement substantially parallel to the longitudinal direction of the belt, a second ply of wire cable reinforcement laid at a bias angle and a third ply of wire cable reinforcement laid at a bias angle. The angle of the third ply cables is larger than that of the second ply in order that the lateral force components of the outer two plies balance each other when being bent around a wheel. Alternatively, the patent discloses a belt with the two outer plies being laid at equal and opposite bias angles, however, the two plies are constructed differently with the third ply having fewer ends than the second ply either by having smaller cables or a lesser number of cables, again to balance the lateral forces exerted by the outer two plies. Producing two plies of different construction is inefficient, costly and can lead to difficulties should they be mistakenly interchanged in a manufacturing operation.
The '498 patent correctly assumes that the tensile cables in the longitudinal direction do not exert a lateral force due to their being bent around a wheel. However, since the tensile cable is commonly spirally wrapped as a practical matter, the cable is not at 0.degree. to the longitudinal direction. When a drive belt is installed on the wheels of a vehicle to be driven by friction, a preload of force is applied to the belt in the longitudinal direction. This force exerts a bending moment on the spirally wrapped cables in the transverse direction as the cables attempt to attain the 0.degree. direction which affects the tracking of the drive belt.